The present invention is directed to a system and method for purifying water. In particular, the invention is directed to a system and method for removing contaminants, such as volatile organic compounds and inorganic compounds like metals, from water through the use of a system and method for heating the water to form vapor and then super heating the vapor to remove contaminants.
Not Applicable.
Many homes, businesses and communities rely on underground water for their fresh water supply. By drilling wells to various depths this underground water which is contained in underground aquifers is tapped and used. This is generally a pure water source, although it may have a relatively high mineral content. That is, the water may be what is commonly termed xe2x80x9chard waterxe2x80x9d.
High mineral content, although bothersome, does not make a water unuseable. However, if water contains measurable levels of organic materials, it can for health reasons, be considered unuseable for human consumption. These organic contaminants are the result of past abuses of the environment, many of them now illegal, that have come to us with our modern way of life. Thus contamination of ground water by volatile and semi-volatile organic compounds has become a widespread and well documented problem.
For example, organic chemicals have been disposed of by depositing them in landfills or by letting them seep into the ground and air from waste lagoons. Such contaminants enter the ground water from various sources such as underground storage tanks, municipal and industrial landfills, and industrial effluents. Contaminants may also enter the water as unintended by-product of conventional chemical treatment processes utilized to disinfect water on its way to municipal water supplies. Gasoline has entered the ground water from corroded underground storage tanks. A corroded tank can leak five or more gallons per day into the ground. This leakage is usually not discovered until hundreds of gallons have leaked into the ground. The result of ground water contamination is that wells which once yielded pure water now only produce contaminated water. Aquifers have been polluted with amounts of organics which make the water under a large area unuseable. However, in many cases the pollution only affects a small area. As the concentration of contaminants in ground water approach or exceed xe2x80x9cacceptable levelsxe2x80x9d, the contaminants must be removed to render the water potable. Hence, as the water supply used by a municipality and/or private well owner approaches the xe2x80x9cacceptable levelxe2x80x9d for a contaminant, the municipality and/or private well owner must either accept the risk associated with such levels of contaminant, locate an alternative water source, or implement a treatment processes for removing the contaminant. Generally, treatment processes for removing contaminants from water are extremely expensive. The most common method of removing contaminants from water is to contact the water with granular activated carbon. Treatment with activated carbon is generally the treatment of choice because it can readily remove a wide variety of typical contaminants. However, while activated carbon is effective at removing the less volatile contaminants such as PCBs, PAHs, and phenolics it is not particularly effective at removing the more volatile contaminants such as chloroform, 1,1,2-trichloroethane and trichloroethylene because of its low affinity for such contaminants. Hence, effective use of activated carbon to treat water contaminated with a volatile contaminant requires frequent replacement of the activated carbon to maintain optimum affinity of the activated carbon for the contaminant. Such frequent replacement of the activated carbon can significantly increases the cost of an already expensive process. A second commonly employed method of removing contaminants from water is to pass the water through an air stripping tower. Basically, an air stripping tower removes contaminants from water by cascading the water over a packing material designed to uniformly disperse the water throughout the tower while providing an upward flow of air which is also designed to uniformly disperse the water throughout the tower as well as provide a supply of air into which the contaminants may dissipate. However, effective operation of air stripping towers is difficult as they are readily susceptible to flow channeling and flooding. Air stripping is the treatment method of choice for removing volatile contaminants from water because of its relatively low cost. However, in order to prevent contamination of the atmosphere with the stripped contaminants it is typically necessary to recover the contaminant from the air prior to its release into the atmosphere and such secondary recovery can significantly increase the cost of the treatment. In addition, air stripping is not particularly effective at removing semivolatile and non-volatile contaminants as such contaminants are not readily volatilized from the water into the air. In the industrial arts, it is known to use an activated carbon filter in combination with a radiation source to filter and purify water. For example, such systems are used in the production of bottled water. The adaptation of this technology to home use has been difficult. Industrial systems are large, expensive and require special knowledge and tools to maintain. The expense of these systems is often due to the fact that they are designed to process water volumes many times larger than those required for home use. Other challenges encountered when designing such a water treatment system for home use stem from the varying operating conditions in each home. For example, water quality, water line pressure, water demand and the sophistication of the user will vary in different homes. Some water purifiers intended for home use are known which combine activated carbon filters with an ultraviolet (UV) radiation source. However, the performance of most known ultraviolet discharge bulb designs degrades with time. It is therefore desirable to monitor the radiant energy source and alert the user if there is a malfunction. In this regard, these home units have had a limited success due to inherent problems with their design that make maintenance of the units by the homeowner difficult and inconvenient. This can result in a water purification unit that, in time, operates only marginally if at all.
Another type of pollution that poses significant health risks is microbiological activity. Like volatile organic pollution, the effects of microbiological activity in water is far more serious than the problems of hard water. Where the water purification unit is being used with a source of drinking water that contains contaminants or microbiological activity, the lack of maintenance of an activated carbon filter can have serious consequences. Thus one important factor is the kill rate of microorganisms, which may vary dependent on the performance of the carbon filter. Such filters are commonly used to remove contaminants from the water prior to irradiation. Moreover, the effectiveness of radiation in the killing of microorganisms is dependent on the clarity of the water. If any significant particulate contamination defeats the carbon filter, such contamination can mask or protect the microorganisms from the killing radiation. The drawbacks associated with the processes commonly employed to remove contaminants from water has resulted in a continued need for an inexpensive alternative technique for achieving the effective removal of contaminants, particularly volatile contaminants, from groundwater. In some circumstances, supplying bottled water may be an option. However, it is often costly, or impossible depending on the intended location. Furthermore, bottled water is not a viable solution for all situations, such as for general usage in the home.
It is therefore desirable to provide some water purification technique which is simple and economical, and which preferably does not require any large, complex or expensive equipment. It is desirable that the method can be carried out in a simple and economic apparatus, so that it becomes feasible to supply such equipment or apparatus to any location where potable water is needed.
The present invention is directed primarily to cleaning water for end use, both residential and commercial, but may also be used for large scale operations, such as the remediation of polluted water from a disaster.
The present invention purifies the water by exposing it to a first heat source to cause the water to change from liquid to a substantially gaseous vapor, thus abandoning any insoluble matter that may have been interspersed in the liquid. The vapor is then super-heated by a second heat source of sufficient magnitude to increase the vapor temperature to a level at which most, if not all remaining contaminants are destroyed. The super-heated vapor condenses to form potable water.
The first heating of the water to vapor may be accomplished by an apparatus that includes a flash-heating device that raises the water temperature above its boiling point almost instantaneously upon entry, thus avoiding any foaming problems that typically lower the efficiency in conventional water boiling tanks. As the water immediately evaporates in the flash-heating device, it forms steam and leaves the insoluble matter behind. The steam is further heated to form a substantially gaseous vapor before being super heated.
While the vapor is in a substantially gaseous form, preferably at a temperature in the range of 212-600xc2x0 F., it is super-heated by a second heat source to a temperature which is preferably in the range of 1500-3000xc2x0 F. This second heat source may be an electrical field of sufficient magnitude. The voltage required for this utility may originate from a power supply, which may be powered by a standard household outlet. Preferably, the electrical field is generated in a chamber having a shape or configuration most conducive to causing ample contact between the vapor and electrical field.
After contact with the electrical field, the super-heated vapor is allowed to condense, forming potable water, and collected for use. Preferably, the present invention is operated at a pressure less than 10 psi.